MELANOCORTIN AND MCH PRECURSOR-DERIVED NEI EFFECTS ON STRIATUM-MIDBRAIN COCULTURES

The possibility of developmental effects of POMC-derived melanocortins and analogs on neurons of fetal rat brain regions exhibiting marked d evelopmental melanocortin receptor expression, was studied in serum-fr ee co-cultures of gestational day 18 striatal and mesencephalic cells, and compared with NEI and NGE. These two peptide fragments of the mel anin concentrating hormone precursor, occurring in brain areas devoid of POMC terminals, cross-react with cu-MSH antibodies; NEI elicits gro oming similar to a-MSH. Neurofilament protein (NF), growth-associated protein (GAP-43) and synaptophysin of the synaptosomal fraction were d etermined by ELISA as markers for neuritogenesis, growth cones, and ne rve terminal differentiation. Cell survival was analyzed by MTT assay, proportions of major cell types by immunocytochemistry. a-Melanocyte- stimulating hormone (a-MSH, effective concentration 250-2500 nM), the analog Nle(4)-, D-Phe(7)-alpha-MSH (NDP, 3.1-750 nM), and NEI (250 nM) increased NF in 3 day cultures by 11%, 17%, and 22%, respectively, wh ereas ACTH(1-24) and ACTH(1-39) (25-2500 nM) were ineffective. In 11 d ay cultures, alpha-MSH (250-750 nM), but not NDP, ACTH(1-24) or ACTH(1 -39), increased synaptosomal synaptophysin by 11%. GAP-43 and cell sur vival remained unaffected. These data indicate that selected melanocor tins as well as NEI can influence differentiation of neural processes in brain neurons. (C) 1998 Elsevier Science Inc.